Dude it's okay, just take the L and say you don't know how vaginas work.

Vaginas are typically self-cleaning.
Fishy smells are caused by infections.
Washing out a vagina disrupts the microbial ecosystem, making it more prone to infections.

Or idk, go wash your eyeballs or smth cause you're worried they'll smell like rotting eggs if you don't, I'm not your mum.